Yes - totally agree. Looking to break out of the ISO performance of my T1i, but it's less about crop vs. FF, and more about what leaps in ISO improvement mean - regardless of format.

But you involved the format, like it or not, in your question. The "ISO performance" is better on FF because of the format, not because of better sensors. And then there are so many other variables. You cannot ignore the format.

Yes - but all indications are that the 7D Mark 2 (available in the next 6-8 months) will have the same ISO performance as the 5D Mark 3.

They have to invent a quantum perpetuum mobile for that - that adds 25% to the light falling on the sensor; and then a sensor which detects it all.

Do not believe all marketing rumors. Canon are known for misleading statements like this, and after the fact they explain that they were talking about NR in the JPEGs.